Sealant for organic EL display element, organic EL display device, and method for manufacturing organic EL display device

Abstract

This encapsulant for an organic EL display element contains a cationic-polymerizable compound, a cationic polymerization initiator, a UV absorber, and a compound having phenolic hydroxyl groups. The mass ratio of the compound having phenolic hydroxyl groups to the UV absorber (compound having phenolic hydroxyl groups / UV absorber) is 0.01 or greater but less than 1.00.

Description

[Technical Field]

[0001] The present invention relates to a sealing material for an organic EL display element, an organic EL display device, and a method for manufacturing an organic EL display device. [Background technology]

[0002] In recent years, organic electroluminescence (EL) displays have become known as image display devices equipped with optical elements. In such image display devices, the optical elements are sealed with a sealing layer to prevent deterioration of the optical elements due to moisture in the atmosphere and the like.

[0003] The sealing layer is formed, for example, by embedding the optical element in a sealing composition and then curing the sealing composition by light irradiation.

[0004] As such a sealing composition, for example, a sealant for an organic EL display element containing a cationically polymerizable compound, a polymerization initiator, and a benzotriazole compound has been proposed (see, for example, Example 1 of Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2021 / 006070 Brochure Summary of the Invention [Problem to be solved by the invention]

[0006] On the other hand, in the sealant for organic EL display elements of Patent Document 1, even weak light such as that from a fluorescent lamp generates an acid from the polymerization initiator (photoacid generator). The acid then continues to polymerize (cure) the sealant for organic EL display elements without being deactivated, resulting in an increase in viscosity. In other words, the sealant for organic EL display elements of Patent Document 1 has a drawback in that it has low stability against white light.

[0007] Furthermore, the cured product of such a sealing composition is required to have high reliability.

[0008] The present invention provides a sealing material for organic EL display elements that has excellent stability to white light and reliability after curing, an organic EL display device that includes a sealing layer made of a cured product of the sealing material for organic EL display elements, and a method for manufacturing an organic EL display device. [Means for solving the problem]

[0009] The present invention [1] is a sealing material for an organic electroluminescent display element, which comprises a cationic polymerizable compound, a cationic polymerization initiator, an ultraviolet absorber, and a compound having a phenolic hydroxyl group, and the mass ratio of the compound having a phenolic hydroxyl group to the ultraviolet absorber (compound having a phenolic hydroxyl group / ultraviolet absorber) is 0.01 or more and less than 1.00.

[0010] The present invention [2] includes the sealing material for an organic EL display element according to the above [1], wherein the cationically polymerizable compound is an epoxy compound and / or an oxetane compound.

[0011] The present invention [3] includes the sealing material for an organic EL display element according to the above [1] or [2], wherein the ultraviolet absorber is a benzotriazole compound or a benzophenone compound.

[0012] The present invention [4] includes the sealing material for an organic EL display element according to any one of the above [1] to [3], in which the content of the ultraviolet absorber is 0.1% by mass or more and 2% by mass or less.

[0013] The present invention [5] includes the sealing material for organic EL display elements according to any one of [1] to [4] above, in which the content of the compound having a phenolic hydroxyl group is 0.01% by mass or more and 0.5% by mass or less.

[0014] The present invention [6] includes the sealing material for an organic EL display element according to any one of the above [1] to [5], which is liquid at 25°C and has a solvent content of 0.05 mass % or less.

[0015] The present invention [7] includes the sealing material for an organic EL display element according to any one of the above [1] to [6], which has a viscosity at 25°C of 5 mPa·s or more and 50 mPa·s or less.

[0016] The present invention [8] includes an organic EL display device comprising a substrate, an organic EL element mounted on one surface of the substrate in the thickness direction, and a sealing layer covering the organic EL element, wherein the sealing layer is made of a cured product of the sealing material for organic EL display elements described in any one of [1] to [7] above.

[0017] The present invention [9] includes a method for manufacturing an organic EL display device, comprising: a first step of preparing a substrate; a second step of mounting an organic EL element on one surface of the substrate in the thickness direction; and a third step of forming a sealing layer that covers the organic EL element by an inkjet method, wherein the sealing layer is made of a cured product of the sealing material for organic EL display elements described in any one of [1] to [7] above. [Effects of the Invention]

[0018] In the organic EL display element sealing material of the present invention, the mass ratio of the compound having a phenolic hydroxyl group to the ultraviolet absorber (compound having a phenolic hydroxyl group / ultraviolet absorber) is 0.01 or more and less than 1.00. In this organic EL display element sealing material, since the mass ratio is 0.01 or more, stability against white light can be improved. Furthermore, in this organic EL display element sealing material, since the mass ratio is less than 1.00, reliability after curing can be improved.

[0019] The organic EL display device of the present invention has an organic EL element covered with a sealing layer made of the cured product of the sealing material for organic EL display elements of the present invention, and therefore has excellent reliability.

[0020] The method for producing an organic EL display device of the present invention uses an inkjet method to form a sealing layer that covers an organic EL element and is made of a cured product of the sealing material for an organic EL display element of the present invention, thereby making it possible to produce an organic EL display device with excellent reliability. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 shows a cross-sectional view of one embodiment of the organic EL display device of the present invention. [Figure 2] 2A to 2C are schematic diagrams showing one embodiment of the method for manufacturing an organic EL display device of the present invention. Fig. 2A shows a first step of preparing a substrate. Fig. 2B shows a second step of mounting an organic EL element on one surface of the substrate in the thickness direction. Fig. 2C shows a third step of forming a sealing layer 3 that covers the organic EL element 2 by an inkjet method. DETAILED DESCRIPTION OF THE INVENTION

[0022] The sealing material for an organic EL display element contains a cationically polymerizable compound, a cationic polymerization initiator, an ultraviolet absorber, and a compound having a phenolic hydroxyl group.

[0023] <Cationic polymerizable compound> Examples of the cationically polymerizable compound include an epoxy compound and an oxetane compound. That is, the cationically polymerizable compound is preferably an epoxy compound and / or an oxetane compound. More preferably, the cationically polymerizable compound is an epoxy compound or an oxetane compound.

[0024] [Epoxy compounds] Examples of epoxy compounds include alicyclic epoxy resins, aliphatic epoxy resins, and aromatic epoxy resins, and preferably alicyclic epoxy resins and aliphatic epoxy resins. More preferably, the epoxy compound includes an alicyclic epoxy resin and an aliphatic epoxy resin, and even more preferably, the epoxy compound consists of an alicyclic epoxy resin and an aliphatic epoxy resin.

[0025] (alicyclic epoxy resin) Alicyclic epoxy resins are curable resins (photocurable resins, preferably ultraviolet curable resins) that have epoxy groups and aliphatic rings (alicyclic skeletons) but do not have aromatic rings.

[0026] Examples of alicyclic epoxy resins include glycidyl group-containing alicyclic epoxy resins, glycidyl ether group-containing alicyclic epoxy resins, and epoxycyclo structure-containing epoxy resins.

[0027] ((Glycidyl group-containing alicyclic epoxy resin)) The glycidyl group-containing alicyclic epoxy resin has, for example, a glycidyl group bonded to an aliphatic ring, and is represented, for example, by the following general formula (1):

[0028] [ka] In formula (1), R1 represents a monovalent organic group, and n represents the degree of polymerization. A substituent such as an alkyl group may be bonded to the carbon atom constituting the cyclohexane ring.

[0029] A specific example of the glycidyl group-containing alicyclic epoxy resin represented by the above general formula (1) is a 1,2-epoxy-4-(2-oxiranyl)cyclohexane adduct of 2,2-bis(hydroxymethyl)-1-butanol.

[0030] The glycidyl group-containing alicyclic epoxy resin represented by the general formula (1) may be a commercially available product, such as EHPE3150 (epoxy equivalent: 170 to 190 g / eq., manufactured by Daicel Corporation).

[0031] ((Glycidyl ether group-containing alicyclic epoxy resin)) The glycidyl ether group-containing alicyclic epoxy resin has glycidyl ether units bonded to an aliphatic ring, and is preferably a polyglycidyl ether-containing alicyclic epoxy resin having a plurality of glycidyl ether units bonded to an aliphatic ring.

[0032] Examples of glycidyl ether-containing alicyclic epoxy resins include difunctional glycidyl ether-containing alicyclic epoxy resins, such as hydrogenated bisphenol A diglycidyl ether, hydrogenated bisphenol F diglycidyl ether, and hexahydrophthalic acid diglycidyl ester.

[0033] ((Epoxy cyclo structure-containing epoxy resin)) The epoxy cyclo structure-containing epoxy resin has an epoxy cyclo structure having an epoxy group composed of two adjacent carbon atoms forming an aliphatic ring and one oxygen atom bonded to those two carbon atoms.

[0034] Examples of epoxy resins containing an epoxycyclo structure include epoxy resins containing an epoxycyclohexane structure (hereinafter referred to as ECH structure-containing epoxy resins).

[0035] Examples of ECH structure-containing epoxy resins include epoxy resins containing one ECH structure as shown in the following chemical formula (2), epoxy resins containing two ECH structures as shown in the following general formula (3), and modified products thereof.

[0036] [ka]

[0037] [ka]

[0038] In formula (3), X represents a linking group (a divalent group having one or more atoms). m represents 0 or 1. R2 represents one atom or substituent selected from the group consisting of a hydrogen atom, a fluorine atom, an alkyl group, a fluoroalkyl group, an aryl group, a furyl group, and a thienyl group. The two R2 in formula (3) may be the same or different.

[0039] An epoxy resin containing two ECH structures represented by the above general formula (3) (hereinafter referred to as an ECH structure-containing epoxy resin represented by general formula (3)) has an ECH structure (epoxycyclohexyl group) at both ends of the molecule, and the two epoxycyclohexyl groups are bonded via a linking group (a carbon-carbon bond when m is 0). The epoxycyclohexyl group is a functional group containing a cyclohexane ring and an epoxy group composed of two adjacent carbon atoms forming the cyclohexane ring and one oxygen atom bonded to those two carbon atoms.

[0040] Examples of the alkyl group represented by R2 in the above general formula (3) include linear or branched alkyl groups having 1 to 6 carbon atoms (e.g., methyl, ethyl, propyl, butyl, pentyl, hexyl, etc.).

[0041] Examples of the fluoroalkyl group represented by R2 in the above general formula (3) include linear or branched fluoroalkyl groups having 1 to 6 carbon atoms (such as perfluoromethyl, perfluoroethyl, and perfluoropropyl groups).

[0042] Examples of the aryl group represented by R2 in the above general formula (3) include aryl groups having 6 to 18 carbon atoms (such as phenyl and naphthyl groups).

[0043] Examples of the linking group represented by X in the above general formula (3) include an oxygen atom, a sulfur atom, a divalent hydrocarbon group, a polyoxyalkylene group, a carbonyl group, an ether group, a thioether group, an ester group, a carbonate group, an amide group, and groups formed by linking these groups. When m is 0, two ECH structures are linked via a carbon-carbon bond.

[0044] Examples of divalent hydrocarbon groups include linear or branched alkylene groups having 1 to 20 carbon atoms (e.g., methylene, methylmethylene, dimethylmethylene, ethylene, propylene, trimethylene, and butylene groups), and linear or branched unsaturated hydrocarbon groups having 1 to 20 carbon atoms (e.g., propenylene, methylpropenylene, and butenylene groups).

[0045] Examples of the polyoxyalkylene group include linear or branched polyoxyalkylene groups having 1 to 120 carbon atoms (such as polyoxyethylene groups and polyoxypropylene groups).

[0046] Specific examples of the ECH structure-containing epoxy resin represented by general formula (3) include (3,3',4,4'-diepoxy)bicyclohexyl, bis(3,4-epoxycyclohexylmethyl)ether, 1,2-bis(3,4-epoxycyclohexane-1-yl)ethane, 2,2-bis(3,4-epoxycyclohexane-1-yl)propane, 3,4-epoxycyclohexylmethyl (3,4-epoxy)cyclohexanecarboxylate, and ε-caprolactone-modified 3',4'-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate, and preferably (3,3',4,4'-diepoxy)bicyclohexyl (in the above formula (3), m is 0 and R2 is a hydrogen atom).

[0047] Commercially available ECH structure-containing epoxy resins represented by the general formula (3) can also be used. Examples of commercially available ECH structure-containing epoxy resins represented by the general formula (3) include Celloxide 8000, Celloxide 8010, Celloxide 2021P, and Celloxide 2081 (all manufactured by Daicel Corporation).

[0048] As the ECH structure-containing epoxy resin, preferably, an ECH structure-containing epoxy resin represented by the above general formula (3) can be used.

[0049] As the alicyclic epoxy resin, preferably, an epoxy cyclo structure-containing epoxy resin is used.

[0050] The weight-average molecular weight of the alicyclic epoxy resin is, for example, 200 or more, and for example, 1000 or less, preferably 500 or less. The weight-average molecular weight (Mw) can be determined by gel permeation chromatography (GPC) using polystyrene as a standard substance (the same applies hereinafter).

[0051] The epoxy equivalent of the alicyclic epoxy resin is, for example, 90 g / eq or more, preferably 100 g / eq or more, and for example, 250 g / eq or less, preferably 190 g / eq or less. The epoxy equivalent can be measured in accordance with JIS K7236:2001 (the same applies hereinafter).

[0052] (aliphatic epoxy resin) Examples of the aliphatic epoxy resin include difunctional aliphatic epoxy resins, such as ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, and neopentyl glycol diglycidyl ether, and preferably neopentyl glycol diglycidyl ether.

[0053] The weight average molecular weight of the aliphatic epoxy resin is, for example, 150 or more and, for example, 400 or less.

[0054] The aliphatic epoxy resin has an epoxy equivalent of, for example, 60 g / eq. or more and, for example, 250 g / eq. or less.

[0055] When the epoxy compound contains an alicyclic epoxy resin and an aliphatic epoxy resin, the content of the alicyclic epoxy resin is, relative to 100 parts by mass of the total amount of the alicyclic epoxy resin and the aliphatic epoxy resin, for example, 10 parts by mass or more, preferably 20 parts by mass or more, and for example, 50 parts by mass or less, preferably 40 parts by mass or less. The content of the alicyclic epoxy resin is, relative to the total amount of the cationically polymerizable compound, for example, 5% by mass or more, preferably 10% by mass or more, and for example, 30% by mass or less, preferably 20% by mass or less.

[0056] When the epoxy compound contains an alicyclic epoxy resin and an aliphatic epoxy resin, the content of the aliphatic epoxy resin is, relative to 100 parts by mass of the total amount of the alicyclic epoxy resin and the aliphatic epoxy resin, for example, 40 parts by mass or more, preferably 50 parts by mass or more, more preferably 60 parts by mass or more, and for example, 90 parts by mass or less, preferably 80 parts by mass or less. The content of the aliphatic epoxy resin is, relative to 100 parts by mass of the total amount of the alicyclic epoxy resin and the aliphatic epoxy resin, for example, 20% by mass or more, preferably 30% by mass or more, and for example, 50% by mass or less, preferably 40% by mass or less.

[0057] The epoxy compounds can be used alone or in combination of two or more.

[0058] The content of the epoxy compound relative to the cationically polymerizable compound is, for example, 30% by mass or more, preferably 40% by mass or more, and for example, 70% by mass or less, preferably 60% by mass or less.

[0059] [Oxetane compounds] The oxetane compound contains, for example, from 1 to 5 oxetane rings.

[0060] Examples of the oxetane compound include monofunctional oxetane compounds having one oxetane ring, bifunctional oxetane compounds having two oxetane rings, and trifunctional or higher oxetane compounds having three or more oxetane rings.

[0061] Examples of monofunctional oxetane compounds include 3-ethyl-3-hydroxymethyloxetane, 3-(meth)allyloxymethyl-3-ethyloxetane, (3-ethyl-3-oxetanylmethoxy)methylbenzene, 2-ethylhexyl(3-ethyl-3-oxetanylmethyl)ether, ethyldiethylene glycol(3-ethyl-3-oxetanylmethyl)ether, and 3-cyclohexylmethyl-3-ethyloxetane.

[0062] Examples of bifunctional oxetane compounds include 1,4-bis{[(3-ethyl-3-oxetanyl)methoxy]methyl}benzene, 3,3'-(oxybismethylene)bis(3-ethyloxetane), 1,4-bis[(3-ethyl-3-oxetanyl)methoxy]benzene, 1,3-bis[(3-ethyl-3-oxetanyl)methoxy]benzene, 3,7-bis(3-oxetanyl)-5-oxa-nonane, 1,4-bis[(3-ethyl-3-oxetanylmeth 1,2-bis[(3-ethyl-3-oxetanylmethoxy)methyl]benzene, 1,2-bis[(3-ethyl-3-oxetanylmethoxy)methyl]ethane, 1,2-bis[(3-ethyl-3-oxetanylmethoxy)methyl]propane, ethylene glycol bis(3-ethyl-3-oxetanylmethyl)ether, and dicyclopentenyl bis(3-ethyl-3-oxetanylmethyl)ether are preferred, and 3,3'-(oxybismethylene)bis(3-ethyloxetane) is preferred.

[0063] Examples of trifunctional or higher oxetane compounds include trimethylolpropane tris(3-ethyl-3-oxetanylmethyl) ether, pentaerythritol tris(3-ethyl-3-oxetanylmethyl) ether, pentaerythritol tetrakis(3-ethyl-3-oxetanylmethyl) ether, and dipentaerythritol pentakis(3-ethyl-3-oxetanylmethyl) ether.

[0064] Commercially available oxetane compounds can also be used. Examples of commercially available oxetane compounds include Aronoxetane OXT-221 (3,3'-(oxybismethylene)bis(3-ethyloxetane)) and Aronoxetane OXT-121 (both manufactured by Toagosei Chemical Industry Co., Ltd.).

[0065] As the oxetane compound, preferably, a bifunctional oxetane compound is used.

[0066] The oxetane compounds can be used alone or in combination of two or more.

[0067] The content of the oxetane compound relative to the cationically polymerizable compound is, for example, 30 mass % or more, preferably 40 mass % or more, and for example, 70 mass % or less, preferably 60 mass % or less.

[0068] The content of the cationically polymerizable compound in the sealing material for organic EL display elements is, for example, 80 mass % or more, preferably 90 mass % or more, and for example, 98 mass % or less.

[0069] <Cationic polymerization initiator> The cationic polymerization initiator is, for example, a photoacid generator that generates an acid upon irradiation with light.

[0070] The cationic polymerization initiator is not particularly limited, and known cationic polymerization initiators can be used.

[0071] The cationic polymerization initiators can be used alone or in combination of two or more kinds.

[0072] The content of the cationic polymerization initiator is, relative to 100 parts by mass of the cationic polymerizable compound, for example, 0.5 parts by mass or more, preferably 0.8 parts by mass or more, more preferably 1.3 parts by mass or more, and for example, 5 parts by mass or less, preferably 2.5 parts by mass or less.

[0073] The content of the cationic polymerization initiator in the sealing material for organic EL display elements is, for example, 0.5 mass % or more, preferably 1 mass % or more, and for example, 10 mass % or less, preferably 5 mass % or less.

[0074] <UV absorber> The ultraviolet absorber is a component that absorbs white light and suppresses the generation of acid from the cationic polymerization initiator.

[0075] Examples of ultraviolet absorbers include benzotriazole compounds, benzophenone compounds, triazine compounds, and cyanoacrylate compounds.

[0076] Examples of benzotriazole compounds include 2-(5-methyl-2-hydroxyphenyl)benzotriazole, 2,2-hydroxy-3,5-bis(α,α-dimethylbenzyl)phenyl, 2-(2'-hydroxy-5'-methyl-phenyl)benzotriazole, 2-(2'-hydroxy-3',5'-di-t-butyl-phenyl)benzotriazole, 2-(2'-hydroxy-3'-t-butyl-5'-methyl-phenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3',5'-di-t-butyl-phenyl)-5-chlorobenzotriazole, 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)-phenol, 2-(2-hydroxy-5-methylphenyl)benzotriazole, and 2-(2'-hydroxy-4'-n-octoxyphenyl)benzotriazole. Preferred examples include 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)-phenol, 2-(2-hydroxy-5-methylphenyl)benzotriazole, and 2-[2-hydroxy-5-[2-(methacryloyloxy)ethyl]phenyl]-2H-benzotriazole. More preferred examples include 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)-phenol and 2-(2-hydroxy-5-methylphenyl)benzotriazole, and even more preferred examples include 2-(2-hydroxy-5-methylphenyl)benzotriazole.

[0077] The benzotriazole compound may be a commercially available product, such as Tinuvin 234 (2-(2H-benzotriazole-2-yl)-4,6-bis(1-methyl-1-phenylethyl)-phenol, manufactured by BASF Japan Ltd.), KEMISORB71 (2-(2-hydroxy-5-methylphenyl)benzotriazole, manufactured by Chemipro Chemical Co., Ltd.), or RUVA-93 (2-[2-hydroxy-5-[2-(methacryloyloxy)ethyl]phenyl]-2H-benzotriazole, manufactured by Otsuka Chemical Co., Ltd.).

[0078] Examples of the benzophenone compounds include [2-hydroxy-4-(octyloxy)phenyl](phenyl)methanone, 2-hydroxy-4-n-octyloxybenzophenone, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxy-5-sulfobenzophenone, 2- Examples of suitable benzophenones include hydroxy-4-methoxy-2'-carboxybenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone trihydrate, 2-hydroxy-4-n-dodecyloxybenzophenone, 2-hydroxy-4-benzyloxybenzophenone, 2,2',4,4'-tetrahydroxybenzophenone, 2-hydroxy-4-dodecyloxybenzophenone, and 2-hydroxy-4-(2-hydroxy-3-methacryloxy)propoxybenzophenone. Preferred examples include [2-hydroxy-4-(octyloxy)phenyl](phenyl)methanone and 2-hydroxy-4-n-octyloxybenzophenone. More preferred examples include 2-hydroxy-4-n-octyloxybenzophenone.

[0079] The benzophenone compound may be a commercially available product, such as KEMISORB12 (2-hydroxy-4-n-octyloxybenzophenone, manufactured by Chemipro Chemicals) or Adekastab 1413 ([2-hydroxy-4-(octyloxy)phenyl](phenyl)methanone, manufactured by ADEKA Corporation).

[0080] Examples of triazine compounds include 2-[4,6-di(2,4-xylyl)-1,3,5-triazin-2-yl]-5-octyloxyphenol and 2,4-diphenyl-6-(2-hydroxy-4-hexyloxyphenyl)-1,3,5-triazine, and preferably 2,4-diphenyl-6-(2-hydroxy-4-hexyloxyphenyl)-1,3,5-triazine.

[0081] Commercially available triazine compounds can also be used, such as KEMISORB102 (2,4-diphenyl-6-(2-hydroxy-4-hexyloxyphenyl)-1,3,5-triazine, manufactured by Chemipro Chemicals).

[0082] An example of a cyanoacrylate compound is ethyl-2-cyano-3-(3',4'-methylenedioxyphenyl)-acrylate.

[0083] As the ultraviolet absorber, preferably, a benzotriazole compound, a benzophenone compound, or a triazine compound is selected, more preferably, a benzotriazole compound or a benzophenone compound, and even more preferably, a benzotriazole compound or a benzophenone compound is selected as the ultraviolet absorber.

[0084] If the ultraviolet absorber is a benzotriazole compound or a benzophenone compound, the stability against white light is even better.

[0085] Particularly preferably, the ultraviolet absorber is a benzotriazole compound, from the viewpoint of further improving the stability against white light.

[0086] The ultraviolet absorbers can be used alone or in combination of two or more kinds.

[0087] The content of the ultraviolet absorber is, for example, 0.05 parts by mass or more, preferably 0.4 parts by mass or more, more preferably 0.8 parts by mass or more, and for example, 2 parts by mass or less, preferably 1.5 parts by mass or less, relative to 100 parts by mass of the cationically polymerizable compound.

[0088] The content of the ultraviolet absorber in the sealing material for organic EL display elements is, for example, 0.1 mass % or more, preferably 0.5 mass % or more, more preferably 0.8 mass % or more, and for example, 2 mass % or less, preferably 1.5 mass % or less, and even more preferably 1.2 mass % or less, from the viewpoint of improving the reliability of the sealing material for organic EL display elements after curing.

[0089] When the content of the ultraviolet absorber is equal to or more than the above lower limit, the stability against white light can be improved.

[0090] Furthermore, if the content of the ultraviolet absorber is equal to or less than the above upper limit, the curability is maintained when cured by irradiation with ultraviolet light.

[0091] <Compounds with a phenolic hydroxyl group> The compound having a phenolic hydroxyl group is a component that captures the acid generated from the cationic polymerization initiator upon irradiation with light.

[0092] The compound having a phenolic hydroxyl group is a compound having one or more phenolic hydroxyl groups in the molecule, and does not include the above-mentioned benzotriazole compounds, benzophenone compounds, triazine compounds, and cyanoacrylate compounds.

[0093] As such a compound having a phenolic hydroxyl group, preferably, a monofunctional phenolic hydroxyl group compound having one benzene ring and the benzene ring having one phenolic hydroxyl group, a bifunctional phenolic hydroxyl group compound having one benzene ring and the benzene ring having two phenolic hydroxyl groups, and a trifunctional or higher phenolic hydroxyl group compound having one benzene ring and the benzene ring having three or more phenolic hydroxyl groups can be mentioned. In other words, the compound having a phenolic hydroxyl group preferably has one benzene ring. This provides excellent stability.

[0094] An example of a compound having a monofunctional phenolic hydroxyl group is a compound represented by the following formula (4). [ka] In the above formula (4), R3 represents a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or an alkyl ester group.

[0095] This represents an alkyl group having 1 to 10 carbon atoms. Examples of the alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, and a decyl group.

[0096] The alkyl ester group is represented by the following formula (5): -R 4 -C(=O)-OR 5 (5)

[0097] In the above formula (5), R4 represents an alkylene group having 1 to 6 carbon atoms. Examples of the alkylene group having 1 to 6 carbon atoms include a methylene group, a methylmethylene group, a dimethylmethylene group, an ethylene group, a propylene group, a trimethylene group, and a butylene group.

[0098] In the above formula (5), R5 represents an alkyl group having 1 to 10 carbon atoms. Examples of the alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, and a decyl group.

[0099] Preferred examples of such compounds having a monofunctional phenolic hydroxyl group include 2,6-di-tert-butyl-p-cresol (a compound in which R3 represents a methyl group in the above formula (4)) and benzenepropanoic acid 3,5-bis(1,1-dimethylethyl)-4-hydroxy-C7-C9 side chain alkyl ester (a mixture of a compound in which R3 represents an alkyl ester group in the above formula (4), and in which R4 represents an ethylene group and R5 represents a heptyl group, a compound in which R4 represents an ethylene group and R5 represents an octyl group, and a compound in which R4 represents an ethylene group and R5 represents a nonyl group in the above formula (5)), and preferably 2,6-di-tert-butyl-p-cresol.

[0100] That is, the compound represented by the formula (4) preferably does not contain an alkyl ester group, and therefore the amount added contributes greatly to the stability under white light, making it even more excellent in terms of achieving both stability under white light and curability.

[0101] Examples of compounds having a bifunctional phenolic hydroxyl group include hydroquinone, resorcinol, tert-butylcatechol, and tert-butylhydroquinone.

[0102] An example of a compound having a tri- or higher functional phenolic hydroxyl group is pyrogallol.

[0103] As the compound having a phenolic hydroxyl group, preferably, a compound having a monofunctional phenolic hydroxyl group and a compound having a bifunctional phenolic hydroxyl group are used, and more preferably, from the viewpoint of achieving both stability to white light and curability, a compound having a monofunctional phenolic hydroxyl group.

[0104] The molecular weight of the compound having a phenolic hydroxyl group is, for example, 94 or more, preferably 100 or more, more preferably 200 or more, and for example, 1000 or less, preferably 500 or less, and from the viewpoint of achieving both stability under white light and curability, more preferably 300 or less. When the molecular weight is small, the amount added contributes greatly to the stability under white light, and therefore, from the viewpoint of achieving both stability under white light and curability, the compound is even more excellent.

[0105] The compound having a phenolic hydroxyl group can be used alone or in combination of two or more kinds.

[0106] The content of the compound having a phenolic hydroxyl group is, relative to 100 parts by mass of the cationically polymerizable compound, for example, 0.01 parts by mass or more, preferably 0.05 parts by mass or more, more preferably 0.08 parts by mass or more, even more preferably 0.1 parts by mass or more, and for example, 0.5 parts by mass or less, preferably 0.3 parts by mass or less, more preferably 0.15 parts by mass or less.

[0107] The content of the compound having a phenolic hydroxyl group in the sealing material for organic EL display elements is, for example, 0.01 mass% or more, preferably 0.05 mass% or more, more preferably 0.08 mass% or more, even more preferably 0.1 mass% or more, and for example, 0.5 mass% or less, preferably 0.3 mass% or less, more preferably 0.15 mass% or less.

[0108] When the content of the compound having a phenolic hydroxyl group is equal to or greater than the above lower limit, the stability to white light can be improved.

[0109] Furthermore, when the content of the compound having a phenolic hydroxyl group is equal to or less than the above upper limit, the curability is excellent.

[0110] The mass ratio of the compound having a phenolic hydroxyl group to the ultraviolet absorber (compound having a phenolic hydroxyl group / ultraviolet absorber) is 0.01 or more, preferably 0.03 or more, more preferably 0.07 or more, even more preferably 0.09 or more, particularly preferably 0.1 or more, and is less than 1.00, preferably 0.5 or less, more preferably 0.3 or less, even more preferably 0.2 or less.

[0111] If the mass ratio is equal to or greater than the lower limit, the stability to white light can be improved.

[0112] On the other hand, if the mass ratio is less than the lower limit, the stability to white light decreases.

[0113] When the mass ratio is equal to or less than the upper limit, the sealing material for an organic EL display element has excellent reliability.

[0114] On the other hand, if the mass ratio exceeds the upper limit, the reliability of the sealing material for organic EL display elements decreases.

[0115] <Preparation of encapsulant for organic EL display elements> To prepare the sealing material for organic EL display elements, first, a cationically polymerizable compound, an ultraviolet absorber, and a compound having a phenolic hydroxyl group are mixed to prepare a mixture. Next, a cationic polymerization initiator is added to the mixture and mixed. This produces a sealing material for organic EL display elements.

[0116] In the above preparation, additives may be blended, if necessary. That is, the sealing material for an organic EL display element may contain additives.

[0117] Examples of the additives include sensitizers, tackifiers, antioxidants, polymerization initiator aids, antioxidants, wettability improvers, surfactants, plasticizers, ultraviolet absorbers, preservatives, and antibacterial agents.

[0118] The blending ratio of the additives is appropriately set depending on the application and purpose.

[0119] The additives can be used alone or in combination of two or more kinds.

[0120] The organic EL display element sealing material may contain a solvent, but preferably does not contain substantially any solvent. Specifically, the solvent content is, for example, 0.05% by mass or less, preferably 0.01% by mass or less, and more preferably 0.001% by mass or less.

[0121] <Physical properties of encapsulant for organic EL display elements> The sealing material for organic EL display elements is preferably liquid at 25° C. Being liquid at 25° C. is defined as having a viscosity of 5 mPa·s or more and 50 mPa·s or less at 25° C. If the sealing material for organic EL display elements is liquid at 25° C., it has excellent inkjet ejection properties.

[0122] The viscosity at 25°C (initial viscosity described below) is, for example, 1 mPa·s or more, preferably 5 mPa·s or more, more preferably 10 mPa·s or more, and for example, 50 mPa·s or less, preferably 30 mPa·s or less, more preferably 25 mPa·s or less.

[0123] The method for measuring the viscosity will be described in detail in the Examples below.

[0124] The cured product of the encapsulant for organic EL display elements preferably has transparency. Specifically, the total light transmittance (based on JIS K 7361-1) of the cured product of the encapsulant for organic EL display elements is, for example, 80% or more, preferably 85% or more, more preferably 90% or more, and for example, 100% or less.

[0125] <Action and effect> In this sealing material for organic EL display elements, the mass ratio of the compound having a phenolic hydroxyl group to the ultraviolet absorber (compound having a phenolic hydroxyl group / ultraviolet absorber) is 0.01 or more and less than 1.00. In this sealing material for organic EL display elements, the mass ratio is 0.01 or more, thereby improving stability against white light. Furthermore, in this sealing material for organic EL display elements, the mass ratio is less than 1.00, thereby improving reliability of the organic EL element after curing from the viewpoint of curability.

[0126] Such an encapsulant for an organic EL display element has excellent stability against white light and reliability after curing, and therefore can be suitably used as an encapsulant for an organic EL display element. In particular, since the encapsulant for an organic EL display element has stability against white light, thickening of the encapsulant is suppressed. Therefore, the encapsulant can be suitably used in an inkjet method.

[0127] <Modification> In the above explanation, to prepare the sealing material for organic EL display elements, first, a cationic polymerizable compound, an ultraviolet absorber, and a compound having a phenolic hydroxyl group are mixed to prepare a mixture, and then a cationic polymerization initiator is added to this mixture. However, it is also possible to add the cationic polymerization initiator all at once together with the cationic polymerizable compound, the ultraviolet absorber, and the compound having a phenolic hydroxyl group.

[0128] <Organic EL display device> An embodiment of the organic EL display device of the present invention will be described with reference to FIG.

[0129] The organic EL display device 10 includes a substrate 1, an organic EL element 2 mounted on one surface of the substrate 1 in the thickness direction, and a sealing layer 3 that covers the organic EL element 2.

[0130] [substrate] The substrate 1 supports the organic EL element 2 .

[0131] The substrate 1 may be, for example, a glass substrate or a plastic substrate, and preferably a glass substrate.

[0132] The thickness of the substrate 1 is, for example, 0.1 mm or more and, for example, 20 mm or less.

[0133] [Organic EL element] The organic EL element 2 is a known organic EL element, and is mounted on the substrate 1. Although not shown, the organic EL element 2 includes a cathode reflective electrode, an organic EL layer, and an anode transparent electrode.

[0134] The sealing layer 3 is a layer for preventing the organic EL element 2 from being deteriorated by moisture in the atmosphere.

[0135] The sealing layer 3 is made of the cured product of the above-mentioned sealing material for an organic EL display element.

[0136] The thickness of the sealing layer 3 is, for example, 1 μm or more and, for example, 100 μm or less.

[0137] <Manufacturing method for organic EL display device> An embodiment of the method for manufacturing an organic EL display device of the present invention will be described with reference to FIGS. 2A to 2C.

[0138] The method for manufacturing an organic EL display device includes a first step of preparing a substrate 1, a second step of mounting an organic EL element 2 on one surface of the substrate 1 in the thickness direction, and a third step of forming a sealing layer 3 that covers the organic EL element 2 by an inkjet method.

[0139] [1st step] In the first step, a substrate 1 is prepared as shown in FIG. 2A.

[0140] [Second process] In the second step, as shown in FIG. 2B, an organic EL element 2 is mounted on one surface of the substrate 1 in the thickness direction by, for example, a known method (for example, vacuum deposition).

[0141] [3rd step] 2C, in the third step, the sealing layer 3 that covers the organic EL element 2 is formed by an inkjet method. By using the inkjet method, the organic EL element 2 can be sealed reliably.

[0142] Specifically, first, an organic EL display element sealing material is disposed by an inkjet method so as to cover the organic EL element 2. Then, the organic EL display element sealing material is irradiated with light to cure the organic EL display element sealing material. In this way, the organic EL display device 10 is manufactured.

[0143] In the organic EL display device 10, the organic EL element 2 is covered with a sealing layer 3 made of a cured product of a highly reliable sealing material for organic EL display elements, and therefore the organic EL display device 10 has excellent reliability.

[0144] Furthermore, in the method for manufacturing an organic EL display device, the sealing layer 3 is formed by an inkjet method, which covers the organic EL element 2 and is made of a cured product of the highly reliable sealing material for an organic EL display element. Therefore, a highly reliable organic EL display device 10 can be manufactured.

[0145] Although not shown, the organic EL display device 10 may also have another sealing layer (for example, an inorganic sealing layer) on one surface in the thickness direction and / or the other surface in the thickness direction. [Example]

[0146] Next, the present invention will be described based on examples and comparative examples, but the present invention is not limited to the following examples. Note that "parts" and "%" are by mass unless otherwise specified. Furthermore, specific numerical values ​​such as blending ratios (content ratios), physical property values, and parameters used in the following description can be substituted with the corresponding upper limit values ​​(numeric values ​​defined as "equal to or less than") or lower limit values ​​(numeric values ​​defined as "equal to or more than" or "exceeding") of the blending ratios (content ratios), physical property values, parameters, etc. described in the above "Form for Carrying Out the Invention."

[0147] <Ingredient details> The trade names and abbreviations of the components used in each example and each comparative example are detailed below. CEL8010: (3,3',4,4'-diepoxy)bicyclohexyl, trade name "Celloxide 8010", manufactured by Daicel Corporation NPG(G): Neopentyl glycol diglycidyl ether, manufactured by Sakamoto Pharmaceutical Co., Ltd. OXT221: 3,3'-(oxybismethylene)bis(3-ethyloxetane), trade name "Aronoxetane OXT-221", manufactured by Toagosei Chemical Co., Ltd. Tinuvin 234: 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)-phenol, manufactured by BASF Japan Ltd. KEMISORB71: 2-(2-hydroxy-5-methylphenyl)benzotriazole, manufactured by Chemipro Chemicals Co., Ltd. RUVA-93: 2-[2-hydroxy-5-[2-(methacryloyloxy)ethyl]phenyl]-2H-benzotriazole, manufactured by Otsuka Chemical Co., Ltd. KEMISORB12: 2-hydroxy-4-n-octyloxybenzophenone, manufactured by Chemipro Chemicals Co., Ltd. Adekastab 1413: [2-hydroxy-4-(octyloxy)phenyl](phenyl)methanone, manufactured by ADEKA Corporation KEMISORB102: 2,4-diphenyl-6-(2-hydroxy-4-hexyloxyphenyl)-1,3,5-triazine, manufactured by Chemipro Chemicals Co., Ltd. BHT: 2,6-di-tert-butyl-p-cresol, molecular weight 220 Irganоx1135: Benzenepropanoic acid 3,5-bis(1,1-dimethylethyl)-4-hydroxy-C7-C9 side chain alkyl ester, molecular weight 390

[0148] <Preparation of encapsulant for organic EL display elements> Example 1 to Example 7 , and Comparative Example 1 to Comparative Example 10 First, a cationically polymerizable compound, an ultraviolet absorber, and a compound having a phenolic hydroxyl group were mixed together to prepare a mixture based on the formulation shown in Table 1. Next, a cationic polymerization initiator was added to the mixture and mixed. This resulted in the preparation of an encapsulant for an organic EL display element.

[0149] <Evaluation> [Stability to white light] The viscosity of the encapsulant for organic EL display elements of each example and each comparative example was measured. Specifically, an E-type viscometer (LV-DV-II+ Pro, manufactured by Brookfield, rotor angle: 1°, rotor radius: 24 mm) was used in accordance with the cone-plate viscometer method of JIS K5600-2-3 (2014). The viscosity (initial viscosity) was measured at 25°C immediately after preparation (within 60 minutes after preparation). The rotation speed of the cone-plate during measurement was 20 rpm.

[0150] Then, 10 ml of this encapsulant for organic EL display elements was weighed into a colorless, transparent 20 ml vial and rotated for 6 hours on a mix rotor placed in a location where the fluorescent light was 600 lux. The viscosity (viscosity after 6 hours) was measured using an E-type viscometer under the same conditions as above.

[0151] The viscosity increase rate was calculated based on the following formula (6). The results are shown in Table 1. Viscosity increase rate = (viscosity after 6 hours / initial viscosity) - 1 (6)

[0152] The stability to white light was evaluated based on the following criteria, and the results are shown in Table 1. ○: The viscosity increase rate was less than 20%. △: The viscosity increase rate was 20% or more and less than 50%. ×: The viscosity increase rate was 50% or more.

[0153] [Coating stability] The organic EL display element encapsulant of each Example and Comparative Example was loaded into an inkjet cartridge DMC-11610 (manufactured by Fujifilm Dimatix Corporation). The inkjet cartridge was set in an inkjet device DMP-2831 (manufactured by Fujifilm Dimatix Corporation) placed under fluorescent lighting. After adjusting the coating conditions, 1000 droplets were applied at 500 μm intervals to a 50 mm × 50 mm non-alkali glass sheet. The organic EL display element encapsulant was then left under fluorescent lighting for 3 hours. Then, using the inkjet cartridge, 1000 droplets were again applied at 500 μm intervals to the non-alkali glass sheet, and the number of droplets that could not be coated was counted. Coating stability was evaluated based on the following criteria. The results are shown in Table 1. ◯: After being left for 3 hours, the number of droplets that could not be applied was 98% or more compared to before being left. Δ: After being left for 3 hours, the number of droplets that could not be applied was 90% or more but less than 98% of that before being left. ×: After being left for 3 hours, the number of droplets that could not be applied was less than 90% of that before being left.

[0154] [Curing rate] (Preparation of evaluation board) The organic EL display element sealing material of each example and each comparative example was loaded into an inkjet cartridge DMC-11610 (manufactured by Fujifilm Dimatix Corporation). The inkjet cartridge was set into an inkjet device DMP-2831 (manufactured by Fujifilm Dimatix Corporation). After adjusting the coating conditions, the material was applied to a 50 mm x 50 mm non-alkali glass panel in a size of 40 mm x 40 mm so that the thickness after curing would be 10 μm. This resulted in a coating film. The coating film was then left for 1 minute in an environment at a temperature of 25°C and humidity of 50%, after which the coating film was irradiated with a UV-LED having a wavelength of 395 nm at an illuminance of 100 mW / cm. 2 , 1500mJ / cm 2 The coating was cured by irradiating it with light of 1000 kJ / cm 2 , thereby producing a substrate for evaluation.

[0155] (Measurement of cure rate) FT-IR measurements were carried out on the sealing materials for organic EL display elements of each of the examples and comparative examples and the evaluation substrate.

[0156] And 1371cm -1 The height of the peak at 831 cm (attributed to the CH stretching vibration) (P1) was used as a reference. -1 The ratio of the heights (P2) of the peaks of the wavenumbers (peaks attributed to epoxy groups) was calculated, and the cure rate was calculated based on the following formula (7). The results are shown in Table 1. {(P2b / P1b)-(P2a / P1a)} / (P2b / P1b)×100 (7)

[0157] In the above formula (7), P1a is 1371 cm after curing -1 P1b indicates the peak height of the wavenumber at 1371 cm before curing. -1 P2a indicates the peak height at 831 cm after curing. -1 P2b indicates the peak height at 831 cm before curing. -1 The wavenumber peak height is shown.

[0158] [Reliability of organic EL elements] The sealing material for organic EL display elements of each example and each comparative example was introduced into an inkjet cartridge DMC-11610 (manufactured by Fujifilm Dimatix Co., Ltd.). The inkjet cartridge was set in an inkjet device DMP-2831 (manufactured by Fujifilm Dimatix Co., Ltd.), and after adjusting the discharge state, the ink was applied to a glass substrate in a size of 15 mm x 15 mm so that the thickness after curing would be 10 μm, thereby obtaining a coating film.

[0159] Next, the coating film was left in an environment of 25°C and 50% humidity for 1 minute, and then irradiated with a UV-LED of 395 nm wavelength at an irradiance of 100 mW / cm 2 , 1500mJ / cm 2 The coating was cured by irradiating it with light of 1000 kJ / cm2 to obtain a cured film.

[0160] The cured film was then subjected to plasma treatment for 1 minute under conditions of 2500 W (ICP power supply), 300 W (RF power supply), DC bias of 200 V, argon (Ar) flow rate of 50 sccm, and pressure of 10 mtorr.

[0161] Thereafter, an inorganic sealing layer (SiNx film) having a thickness of 100 nm was formed on the cured film side by RF sputtering using a SiNx target, thereby producing a first evaluation substrate.

[0162] Separately, an organic EL element was mounted on another glass substrate to produce a second evaluation substrate. The first evaluation substrate and the second evaluation substrate were then bonded together to produce an organic EL display device for evaluation.

[0163] Next, a reliability test was performed on the evaluation organic EL display devices at 85° C. Specifically, the light-emitting area ratio (%) of each evaluation organic EL display device after storage at 85° C. for 100 hours was determined by the following method: That is, using Motic Images Plus software (manufactured by Shimadzu Rika Corporation), the light-emitting area in the initial state and the light-emitting area after storage for 100 hours were calculated, and the light-emitting area ratio was calculated based on the following formula (8). Luminous area ratio (%) = Luminous area after 100 hours storage / Luminous area in the initial state × 100 (8)

[0164] The reliability of the organic EL device was evaluated based on the following criteria, and the results are shown in Table 1. ◯: The light-emitting area ratio was 80% or more. △: The light-emitting area ratio was 50% or more and less than 80%. ×: The light-emitting area ratio was less than 50%.

[0165] [Table 1]

[0166] The above invention is provided as an exemplary embodiment of the present invention, but this is merely an example and should not be interpreted as limiting. Modifications of the present invention that are obvious to those skilled in the art are intended to be included in the scope of the following claims. [Industrial Applicability]

[0167] The sealing material for an organic EL display element, the organic EL display device, and the method for producing an organic EL display device of the present invention are suitably used in the production of image display devices. [Explanation of symbols]

[0168] 1 board 2. Organic EL elements 3. Sealing layer 10 Organic EL display device

Claims

1. a cationically polymerizable compound; a cationic polymerization initiator; an ultraviolet absorber; a compound having a phenolic hydroxyl group, a mass ratio of the compound having a phenolic hydroxyl group to the ultraviolet absorber (compound having a phenolic hydroxyl group / ultraviolet absorber) is 0.01 or more and less than 1.00, the ultraviolet absorber comprises a benzotriazole compound, the benzotriazole compound comprises 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)-phenol or 2-(2-hydroxy-5-methylphenyl)benzotriazole; The sealing material for an organic EL display element, wherein the compound having a phenolic hydroxyl group contains 2,6-di-tert-butyl-p-cresol.

2. 2. The sealing material for an organic EL display element according to claim 1, wherein the cationically polymerizable compound is an epoxy compound and / or an oxetane compound.

3. 2. The sealing material for organic EL display elements according to claim 1, wherein the ultraviolet absorber is a benzotriazole compound containing 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)-phenol or 2-(2-hydroxy-5-methylphenyl)benzotriazole.

4. 2. The sealing material for an organic EL display element according to claim 1, wherein the content of the ultraviolet absorber is 0.1% by mass or more and 2% by mass or less.

5. 2. The sealing material for an organic EL display element according to claim 1, wherein the content of the compound having a phenolic hydroxyl group is 0.01% by mass or more and 0.5% by mass or less.

6. It is liquid at 25°C, The sealing material for an organic EL display element according to claim 1 , wherein the solvent content is 0.05% by mass or less.

7. 2. The sealing material for an organic EL display element according to claim 1, which has a viscosity at 25°C of 5 mPa·s or more and 50 mPa·s or less.

8. A substrate; an organic EL element mounted on one surface of the substrate in the thickness direction; a sealing layer that covers the organic EL element, An organic EL display device, wherein the sealing layer is made of a cured product of the sealing material for an organic EL display element according to claim 1 .

9. A first step of preparing a substrate; a second step of mounting an organic EL element on one surface of the substrate in the thickness direction; and a third step of forming a sealing layer that covers the organic EL element by an inkjet method. The method for manufacturing an organic EL display device, wherein the sealing layer is made of a cured product of the sealing material for an organic EL display element according to claim 1 .

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